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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        kernel-team@fb.com, mingo@kernel.org
Cc:     elver@google.com, andreyknvl@google.com, glider@google.com,
        dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com,
        Mark Rutland <mark.rutland@arm.com>,
        "Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH kcsan 1/8] kcsan: Improve some Kconfig comments
Date:   Wed, 21 Jul 2021 14:08:05 -0700
Message-Id: <20210721210812.844740-1-paulmck@kernel.org>
In-Reply-To: <20210721210726.GA828672@paulmck-ThinkPad-P17-Gen-1>
References: <20210721210726.GA828672@paulmck-ThinkPad-P17-Gen-1>
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From: Marco Elver <elver@google.com>

Improve comment for CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE. Also shorten
the comment above the "strictness" configuration options.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/Kconfig.kcsan | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 0440f373248eb..6152fbd5cbb43 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -40,10 +40,14 @@ menuconfig KCSAN
 
 if KCSAN
 
-# Compiler capabilities that should not fail the test if they are unavailable.
 config CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE
 	def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-compound-read-before-write=1)) || \
 		 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-compound-read-before-write=1))
+	help
+	  The compiler instruments plain compound read-write operations
+	  differently (++, --, +=, -=, |=, &=, etc.), which allows KCSAN to
+	  distinguish them from other plain accesses. This is currently
+	  supported by Clang 12 or later.
 
 config KCSAN_VERBOSE
 	bool "Show verbose reports with more information about system state"
@@ -169,13 +173,9 @@ config KCSAN_REPORT_ONCE_IN_MS
 	  reporting to avoid flooding the console with reports.  Setting this
 	  to 0 disables rate limiting.
 
-# The main purpose of the below options is to control reported data races (e.g.
-# in fuzzer configs), and are not expected to be switched frequently by other
-# users. We could turn some of them into boot parameters, but given they should
-# not be switched normally, let's keep them here to simplify configuration.
-#
-# The defaults below are chosen to be very conservative, and may miss certain
-# bugs.
+# The main purpose of the below options is to control reported data races, and
+# are not expected to be switched frequently by non-testers or at runtime.
+# The defaults are chosen to be conservative, and can miss certain bugs.
 
 config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
 	bool "Report races of unknown origin"
-- 
2.31.1.189.g2e36527f23